ubase/su.c

/* See LICENSE file for copyright and license details. */
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <pwd.h>
#include <grp.h>
#include <shadow.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "config.h"
#include "util.h"

extern char **environ;

static int dologin(struct passwd *);

static void
usage(void)
{
	eprintf("usage: %s [-lp] [user]\n", argv0);
}

static int lflag = 0;
static int pflag = 0;

int
main(int argc, char *argv[])
{
	char *usr = "root", *pass, *cryptpass;
	char *shell;
	struct spwd *spw;
	struct passwd *pw;
	char *newargv[2];
	uid_t uid;

	ARGBEGIN {
	case 'l':
		lflag = 1;
		break;
	case 'p':
		pflag = 1;
		break;
	default:
		usage();
	} ARGEND;

	if (argc < 1)
		;
	else if (argc == 1)
		usr = argv[0];
	else
		usage();

	errno = 0;
	pw = getpwnam(usr);
	if (errno)
		eprintf("getpwnam: %s:", usr);
	else if (!pw)
		eprintf("who are you?\n");

	switch (pw->pw_passwd[0]) {
	case '!':
	case '*':
		eprintf("denied\n");
	}

	/* Empty password? Su now */
	if (pw->pw_passwd[0] == '\0')
		goto dosu;

	uid = getuid();
	if (uid) {
		pass = getpass("Password: ");
		putchar('\n');
		if (!pass)
			eprintf("getpass:");
	}

	if (pw->pw_passwd[0] == 'x' && pw->pw_passwd[1] == '\0') {
		errno = 0;
		spw = getspnam(usr);
		if (errno)
			eprintf("getspnam: %s:", usr);
		else if (!spw)
			eprintf("who are you?\n");

		switch (spw->sp_pwdp[0]) {
		case '!':
		case '*':
			eprintf("denied\n");
		}
		if (uid) {
			cryptpass = crypt(pass, spw->sp_pwdp);
			if (!cryptpass)
				eprintf("crypt:");
			if (strcmp(cryptpass, spw->sp_pwdp) != 0)
				eprintf("incorrect password\n");
		}
	} else {
		if (uid) {
			cryptpass = crypt(pass, pw->pw_passwd);
			if (!cryptpass)
				eprintf("crypt:");
			if (strcmp(cryptpass, pw->pw_passwd) != 0)
				eprintf("login failed\n");
		}
	}

dosu:
	if (initgroups(usr, pw->pw_gid) < 0)
		eprintf("initgroups:");
	if (setgid(pw->pw_gid) < 0)
		eprintf("setgid:");
	if (setuid(pw->pw_uid) < 0)
		eprintf("setuid:");

	if (lflag) {
		return dologin(pw);
	} else {
		shell = pw->pw_shell[0] == '\0' ? "/bin/sh" : pw->pw_shell;
		newargv[0] = shell;
		newargv[1] = NULL;
		if (!pflag) {
			setenv("HOME", pw->pw_dir, 1);
			setenv("SHELL", shell, 1);
			if (strcmp(pw->pw_name, "root") != 0) {
				setenv("USER", pw->pw_name, 1);
				setenv("LOGNAME", pw->pw_name, 1);
			}
		}
		if (strcmp(pw->pw_name, "root") == 0)
			setenv("PATH", ENV_SUPATH, 1);
		else
			setenv("PATH", ENV_PATH, 1);
		execve(pflag ? getenv("SHELL") : shell,
		       newargv, environ);
		weprintf("execve %s:", shell);
		return (errno == ENOENT) ? 127 : 126;
	}
	return EXIT_SUCCESS;
}

static int
dologin(struct passwd *pw)
{
	char *shell = pw->pw_shell[0] == '\0' ? "/bin/sh" : pw->pw_shell;
	char *term = getenv("TERM");
	clearenv();
	setenv("HOME", pw->pw_dir, 1);
	setenv("SHELL", shell, 1);
	setenv("USER", pw->pw_name, 1);
	setenv("LOGNAME", pw->pw_name, 1);
	setenv("TERM", term ? term : "linux", 1);
	if (strcmp(pw->pw_name, "root") == 0)
		setenv("PATH", ENV_SUPATH, 1);
	else
		setenv("PATH", ENV_PATH, 1);
	if (chdir(pw->pw_dir) < 0)
		eprintf("chdir %s:", pw->pw_dir);
	execlp(shell, shell, "-l", NULL);
	weprintf("execlp %s:", shell);
	return (errno == ENOENT) ? 127 : 126;
}